In a known steam pressure cooker as disclosed in European Patent No. 0108203 B1, following a significant pressure reduction by means of the pressure discharge valve, the lid is opened by the dome being initially pressed downwards until locking or blocking members acting between the dome and the angle profile ring also referred to as a frame, become disengaged and then the dome is turned relative to the frame for the radial opening displacement of the clips by means of the grip or handle. In order to be able to rotate the dome relative to the frame, the frictional forces keeping the frame stationary on the cooker must in all circumstances be higher than the frictional forces to be overcome for turning the dome, because otherwise the lid cannot be brought into the open position. It can prove difficult to maintain such friction ratios in a reproducible manner under all operating conditions.
On closing the cooker by oppositely directed rotation of the same with respect to the frame corresponding ratios occur. Following the closing of the clips the blocking members comprising pins and bores must be turned precisely back into the aligned position, so that the dome is again applied to the seal. If this relative setting of dome and frame is not successful, then the steam pressure cooker is not tight, so that no pressure can build up within the cooker. Another in this known steam pressure cooker is that water can penetrate though open gaps between the dome and the frame, as well as between the dome and the seal, and into the interior of the cooker when the lid is cooled under tap water prior to opening.